Better Kitbashing and Asset Management flow, with multiple kits? Organize and browse assets?
External solutions or addons are the way to go. My method was to experiment all the tools I could find that could deal with problems (1) and (2) described in the topic, with special care in which tool would allow to manage, browse and quickly drop big kitbashing kits into Blender.
The two final solutions that &quot;passed the tests&quot; are:
Connecter (https://www.designconnected.com/connecter/)
From their website:

Free and visual creative assets management for 3d, AEC and design professionals.

Connecter consists of two components:

A native Desktop software, where you catalog assets of all kinds, by folders, tags and more. It supports all 3D formats, including .blend files natively as well textures, materials, videos, and more.
A Blender add-on, which allows you to tag objects directly in Blender to be added to Connecter and also to RECEIVE INCOMING DROPS from Connecter, and this is where it shines in terms of asset management for Blender.
Video showing the process with Blender on Youtube.


Asset Management (https://gumroad.com/l/asset_management)
This is a paid Blender addon that adds a &quot;Content Browser&quot; into Blender, for all kinds of assets.

Its biggest advantage is that it's made for Blender only, so you can expect tight integration with all kinds of Blender objects and data.
The disadvantage is that you can't manage the assets outside Blender and you can't have other model formats (fbx, etc). You have to convert everything to a friendly Blender format.